Heretofore coiled spring guidewires have been widely used for facilitating insertion of catheters into a blood vessel. Catheters are generally hollow, flexible tubes generally used to convey fluid to or from a desired body location. Some catheters are capable of being preformed to various shapes which best conform to their anticipated environment.
Often, a catheter insertion procedure is followed. Such procedure includes the first step of inserting an obdurated hollow needle into the body with the object of locating the needle tip in the target vessel. The location of this needle tip is confirmed by removing the obdurator while preparing to insert a coiled spring through the open hollow needle.
After insertion of the coiled spring guidewire through the needle, so that the guidewire extends a short distance distally beyond the needle tip, the needle is withdrawn proximally from the body and the guidewire.
A dilator, of greater diameter and length than the needle, is then substituted for the needle by being inserted into the body surrounding the guidewire, for nearly the length of the dilator.
Next the guidewire is advanced through the length of the dilator until it extends for a distance beyond it. At this point, the guidewire is relatively secure within the blood vessel and the dilator is withdrawn.
The catheter is next inserted over the guidewire and advanced slightly beyond the guidewire. A stylet or the equivalent is often inserted into the lumen defined by helical coils of the guidewire to impart a given form and a given stiffness to the guidewire and therefor to the catheter. The catheter and the guidewire, which may include a stylet, are further inserted into the vessel until an obstruction is encountered.
Obstructions are typically due to narrowing of the vessel opening or the vessel curvature. If the nature of the vessel obstruction is unknown or unanticipated, the catheter may be left in place while the guidewire, with stylet, is withdrawn and a radio opaque dye is injected to assist in determining the nature of the obstruction. A stylet of a differing stiffness or form may be employed to assist in navigating the obstruction.
After an obstruction is encountered, the guidewire is advanced only slightly beyond the distal end of the catheter where it can assume an arcuate shape appropriate to navigate the obstruction encountered. The guidewire is then caused to assume the arcuate shape and the obstruction is navigated. Then the catheter is advanced over the guidewire and the guidewire with the catheter are simultaneously advanced.
In most circumstances, the guidewire need not be advanced to the desired location before being withdrawn. The catheter frequently possesses sufficient longitudinal stiffness to allow direct manipulation of the catheter for the final stage of catheter insertion to the desired location.
It is desirable in using such a coiled spring guidewire to provide some means to allow the tip of the guidewire to deflect to facilitate movement of the guidewire around or through a curved or narrowed path in the vessel.
There have been a number of proposals for different tip constructions which will provide a deflectable tip in a coiled spring guidewire and related devices.
U.S. Pat. No. 4,554,929 to Samson et al. discloses a CATHETER GUIDE WIRE WITH SHORT SPRING TIP AND A METHOD OF USING THE SAME. The spring tip surrounds a reduced section extension of a guidewire shaft.
U.S. Pat. No. 4,498,482 to Williams discloses a TRANSVENOUS PACING LEAD HAVING IMPROVED STYLET. The stylet has a constant diameter at its proximal end, a ball at its distal end and a tapered section in the transition of the stylet from a constant diameter to the ball portion.
U.S. Pat. No. 4,456,017 to Miles discloses a COILED SPRING GUIDE WITH DEFLECTABLE TIP. Its core wire has a reduced section at its distal end which is permanently, and eccentrically, affixed to a head member. Proximal movement of the core wire causes the guide to assume an arcuate shape.
U.S. Pat. No. 4,454,888 to Gold discloses a CARDIAC PACING LEAD WITH CURVE RETAINER. A flat spring near its distal end causes the lead to assume a J-shape when a stylet is withdrawn from that portion of the lead.
U.S. Pat. No. 4,271,847 to Stokes discloses a TEMPORARY ADJUSTABLE BIPOLAR LEAD including a coaxial sliding pacing lead for establishing a connection between a chamber of a heart and a pulse generator.
U.S. Pat. No. 2,024,982 to Scott discloses a SURGICAL INSTRUMENT including a flat tapered stylet.
United Kingdom Patent Application No. 2,064,963A describes a STYLET having a tapered portion terminating at a ball in its distal end and is related to U.S. Pat. No. 4,498,482 referred to above.
Swedish Pat. No. 193885 discloses A CATHETER INTENDED FOR INTRAVASCULAR CATHERIZATION having an arcuately curved distal end which is straightenable by an inserted stylet. The stylet has a rounded cylindrical distal end portion.
However, none of the foregoing patent publications disclose a multi-mode guidewire which provides a varying degree of flexibility at varying longitudinal locations of the guidewire.